U.S. Pat. No. 4,568,113 ('113 patent) discloses and claims a threaded connection for use in tubular goods of bimetallic construction used in the production of oil and gas. The threaded connection of the '113 patent comprises a continuous helical thread having a first straight, untapered portion and a second, tapered portion. The threaded connection of the '113 patent further comprises a coupling having first and second box connections for receipt of first and second pins. When made up, the noses of the pins either abut and seal on each other or abut against a removable washer disposed intermediate the coupling.
The pin noses of the '113 patent have thread-free sections which, when the connection is made up, engage complementary thread-free sections formed in the box of the connection. This engagement of this thread-free surface ostensibly results in a metal-to-metal seal. Although a commercial version of the threaded connection shown in the '113 patent was marketed, it met with limited success because of the fact that it was not gas tight when subjected to high gas pressures, and cycled between tension and compression. The commercial version is discussed in a paper entitled “A Casing Connection For Energy Storage” present at the Solution Mining Research Institute Meeting, Denver, Colo., Oct. 16-19, 1983.